Continuous furnace



oct. e, 193s. w. A. Momo@ Er AL 2,056,904*

CONTINUOUS FURNACE Filed July 10, 1934. 2 Sheets-Sheet 1 Oct. 6, 1936.w. A. MoRToN ET AL CONTINUOUS FURNACE Filed July l0, 1934 2 Sheets-Sheet2 Patented Oct. 6, 1936 UNITED STATS PAE carica 2,056,964 CONTINUOUSFUBNACE Pennsylvania Application .my 16, 1934, sensi No. remco is o im.aai

This invention relates to method of and apparatus for continuous anduniform heating of slabs, billets. blooms or the like, and it is amongthe obiects thereof to provide a furnace design 5 which embodies animproved firing and heat control system.

In the vart of heating by continuous processes asA heretofore practiced,it has been customary to fire the furnace at numerous points and in mostinstances at spaced longitudinal intervals, the furnace being dividedfor that purpose into a so-called heating and soaking chamber, thus esetablishing multiple heatzones of diierent temperatures. Such division offurnace heating l5 chambers was accomplished by the employment of aroof` structure having a drop or partition member that provided for arelatively long heating chamber and short soaking chamber, each of whichwas individually red by regulable burners. In accordance with thepresent invention, a furnace construction embodying a single or unitheating chamber is utilized and the application of the heating medium tothe slabs or billets to bring them up to the necessary working orrolling temperature is accomplished in a novel manner to obtain thedesirable input of h eat without exposing any. portion of the billets toexcessive oxidizing or scaling temperatures, and by means of whichmaximum heating capacity is obtained.

Another object of the invention is the provision of means for preventingthe infiltration of air at the discharge end of the furnace thereby, ineuect,

producing a reducing atmosphere at the point of' maximum temperature toprevent scaling.

,Stilla further object .of the invention is .the provision of means forutilizing different fuels in conjunction with recuperator structureswhich are adapted to develop and maintain a high preheat' of the air'directed to the combustion zone.

49 Still another object 'of the invention is the provision o f means forrecirculating a part of the preheated air through the recuperatorstructure Whereg'ases-of -low B. t. u. value are utilized as fuelthereby lsubstantially reducing the temperature differential betweenpreheated air and waste gases in the walls of the recuperator tile.

Still a' further object of the invention is the l provision of means forheating light billets or the like which controls the temperature at thecharg- 50 ing and dischargingends of the furnace chamber by directingthe heat name or products of combustion from a single iirlng sourcewhereby great flexibility of heat control is provided.

' These and other objects of the invention will become more apparentfrom a consideration of the accompanying drawings constituting a parthereof in lwhich like reference characters designate like parts and inwhich:

Fig. l-is a vertical cross-sectional view longitudinally of a continuousheat furnace embodying u the principles of this invention;

Fig. 2 a horizontal section taken along the line 3 2, Fig. l;

Fig. 3 a vertical section transversely of the furnace taken along theline 3 3, Fig. 1; and 10 Fig. a a horizontal cross-sectional view takenalong the line d-, Fig. 1.

With reference to the several figures of the drawings, the structuretherein illustrated comprises a heating chamber generally designated byl5 the reference numeral i having a constricted charging end 2 anddischarge passage 3; material such asbiiletsor slabs i being supportedvon skid rails or water cooled pipes 5 and moved through the furnace bymeans of a pusher mechanism 6, 2o when the gate 'l .is opened. As'thebillets advance toward the discharge end of the furnace, they travelfrom the rails 5 onto a solid uniformly heated hearth portion d. Thehearth 8 is provided with aslopingend 9 which, with a tapered 25 roof.portion l0 of the heating chamber, forms the discharge passage 3 thatis. controlled by a gate il, the billets being received on a feed-rolltable i2 by which they are conveyed to the rolling mill. The door mechaw1 o. are operated in timed relaso tion with the pusher mechanism 6 sothat the doors open only as a billet is being charged and dischargedintoand out of the furnace.

The tapered roof portion it atthe discharge end of the furnace extendsto a roof i3 which 35 is a dat arch asshown'in Fig. 3 and4 graduallyslopes downwardly towards the charging end 2 of the chamber. A ber porti4 is provided adjacent theapex of the sloping roof portions andVburnersuldfbeneathvthe billets for the bottom 40 heating 'ci'. heavystock, there being as manyiburners or ports providedl transversely ofthe hearth as to supply a heat name of the width of the iurnace. Thesloping hearth portion 9 adjacent the discharge end of the fur- 45 naceis provided with an exhaust passage l5, and exhaust pwages la and'i'lare 'provided beneath the billet supporting rails :5, passages l5. I6and il communicating with recuperator structures i8 and I9 that areseparated by a partition wall20. 50 n Dampers iba and ita are providedfor passages I5 and it to independently regulate the with drawal of theproducts of combustion through these passages,- and a damper 2i controlsexhausti'on of the gases from the furnace chamber di- 56 rectly to astack passage 22 to provide additional means to maintain desirable heatcondition within the recuperator structure.

The arrangement of the recuperator chambers is more clearly shown inFigs. 2 to 4 inclusive of the drawings in which they are shown dividedby the walls 28 and 23, and walls 24 and 25, the latter being providedwith openings 28 through which preheated air is conducted to alongitudinal passage 21 and thence to a transverse passage 28. The heatexchange tile 28 is built up in the recuperator chambers, the tileforming vertical waste gas passages and horizontal-air passages, the airpassages being connected at the bottom with a manifold 30 havingconduits 3| extending to the bottom of the recuperator tile, eachconduit being provided with a damper or gate 32 to regulate the quantityof air entering the different portions of the recuperator structures.

Manifold 30 has a transverse main 33 which is connected to a blower 34,the blower being also provided with a conduit 35 leading to thetransverse passage 28. The preheated air passes upwardly from wpassage28 through conduit 3,6 to a burner 31 extending into the ring port I4 onthe roof of the furnace. Gas ducts or mains 38 and 39 communicate withthe burner 31, the duct 38 being of the lesser diameter as it supplies anatural rich fuel gas while the duct 38 is considerably larger to supplya greater volume of fuel gas such as producer gas that is of a lower B.t. u. value than the natural gas and consequently used in greatervolume.

A blower 34 is'provided with a gate valve 48 that regulates the volumeof air conducted to the manifolds 30 on the sides of the recuperatorsand a gate valve 4I for regulating the amount of preheated air drawnfrom the transverse passage 28 for recirculating with the cold air drawnin through the passage controlled by the gate valve 48 for the purposeto be hereinafter explained.

The waste gases withdrawn from the furnace I through the exhaust passageI5 pass into the recuperator chamber |8 thence downwardly through thevertical .tile passages 42..,to a horizontal passage 43 leading to theexhaust stack passage 44. Passage 43 is controlled by a gate 45.Similarly,'the products of combustion exhausted through the passages I5and I1 may be drawn directly to the stack passage 22 controlled by thegate 2|, or by closing gate 2| the exhaust gases may be drawn throughthe vertical recuperator tile passages 42 to an exhaust passage 48leading to a stack passage 41 that is controlled by a gate 48.

One of the features of the invention is the location of the dischargepassage 3 below the horizontal plane of the furnace hearth 8'and alsobelow the opening of the exhaust passage I5. By so locating thedischarge passage beneath the hearth and exhaust passage, infiltrationof air is prevented. Any' air passing into the discharge passage when,for example, the gate |I is open,

will be drawn through exhaust passage I5 and be prevented fromcontacting the heated billets supported on the hearth 8. By preventinginfiltration of air, scale and oxidization are largely.

eliminated and the withdrawal of air through the exhaust passage I5produces a. reducing. atmosphere in the portion of the furnaceimmediately ladjacent the discharge passage 3.

The method of nring the furnace and regulanon ofthe appncauon nf neat tothe muets together with the control of the furnace tempera- 7 turethrough regulation of the exhaust, and the intensity and volume of thepreheated air is as follows: The gaseous fuel is supplied through thehearth 8 at substantially its termination with the billet supportingskid rails 5. When the burner vis first ignited, the exhaust I5 is shutoff either through manipulation of the damper I5a or by closing gate 45so that all of the heat is drawn beneath the long sloping roof portiontowards the charging end of the furnace, damper Ilia likewise being shutoif or closed for the initial heating of the furnace. Roof I3 isinclined or sloped as shown in Fig. 1 to reduce the volume of theproducts of combustion toward the charging end ofthe furnace to obtainuniform heating* by lowering the level of movement of the gases as theypass to the exhaust opening I1. As the furnace chamber is brought up totemperature, billets 4 are charged into the heating chamber by thepusher mechanism 8, eachsuccessive stroke of the pusher advancing thebillets along the rail 5 a distance corresponding to the width of thebillet, and as they approach the firing ports they will be subjected tomaximum heat. On account of the water cooled rails 5 producing coldspots or dark spots on the bottom of the billet, the solid hearthportion 8 is provided to uniformly heat the zol billet before beingpushed over the inclined slope 8 of the discharge passage 3.

Dampers I5a and IGa are subsequently opened and gates 48 and 45 arewholly 'or partially opened while gate 2| is wholly or partially closed.Instead of the products of-'combustion passing longitudinally of thefurnace to the exhaust I1 and thenceto the stack, they will partially bedrawn to the exhaust passage I5 and may be partially withdrawn at themid-portion of the heat-- ing chamber through the passage I6 andpartiallly withdrawn through the end passage I1 thence through the tilestructures of recuperator chambers I8, I9 and Isa, and through'theirrespective stack passages 43 and 45.

Blower 34 is placed in operation and the gate 48 is opened an amount tosupply a desired quantityof air to the manifolds 30 from which it isconducted through the gate controlled conduits 3| to the air passages ofthe recuperators. The air, as it is preheated, rises in the tilestructure and passes through 'openings 28 of the recuperator walls 25into the collecting air passage 21thence to the transverse air passage28 4upwardly through conduits 36 to the burner 31. It is to be notedthat after the preheated air leaves the recuperator tile passages, heatlosses by radiation are prevented and it is further heated in thehorizontal collecting passage 21 which is adjacent the hottest portionof the waste gas tile passage of the recuperator and beneath the exhaustpassages I5 and I6.

Provision is also made for recirculating a part of the preheated airwhen the leaner fuel gases such as producer gas is employed. That is tosay, if air is supplied to vthe recuperators in quantities adequate tosupport combustion whena rich natural gas is employed, a lesser quantityof air is necessary where gases such as producer gases of lower- B. t.u. are fired in the furnace. At the same time, it isnecessary tomaintain sunlciently low temperatures of the recuperator tile to preventoverheating and breakage of the tile and to accomplish this a part ofthe preheated air is recirculated by exhausting the excess portion usedfor rich fuel from the transverse passage 28 through the blower conduit'35, this being accom- 2,056,904 plighed by opening the gate M andregulating the gate 40 so a lesser quantity of cold air is drawn intothe blower. By thus recirculating the air, the temperature differentialbetween the inner and 5 outer walls of the bottom recuperator tiles issubstantially reduced or eliminated and a high preheat of air ismaintained at the burner port.

By the arrangement of exhausting the products of combustion at the rearand front portion of l the heating chamber and ring at an intermediatepoint between the charging end and discharging end, high flametemperatures may be directed to the billets greatly in excess of thennal rolling temperature of the billets Without 15 heating the billetsbeyond the desired rolling temperature, thereby accelerating the heatingand increasing the capacity of the furnace. By proper regulation of theexhaust through passage l5, loss of heat is prevented once th'e billetshave 20 been brought up to suitable rolling temperatures.

By means oi.' the intermediate exhaust passage i6, the .waste gastemperatures may be controlled for any desired heating rate. Cold steelentering the furnace has a higher temperature differ- 25 ential with thewaste gases than the steel in the area adjacent the exhaust passage i6and by manipulation of the dampers, this heat 'differential may bereduced at the charging end and increased above the ordinary in theintermediate 30 area so that more uniform heat absorption prevails alongthe hearth.

Accordingly, by means of the exhaust passage i6, temperaturedifferential and the heat rate along the hearth is balanced orcontrolled to 35 maintain a more nearly constant condition. When moreheat is drawn down passage I6 as a result of increased tonnage, thetemperature in the recuperator is increased, and increased air ,preheattemperatures follow. This automatical- 40 ly increases the flametemperature above the solid hearth portion and assists in maintainingthe desired temperature differential by which the heat rate may beaccelerated.

By dividing the heat exchangers into groups 4'5 of chambers withseparate damper control, more effective regulation of the heat in thefurnace is attainable. Also by the employment of the unit heatingchamben. the furnace is particularly adapted to thevuse of producer gasfuel which does not efciently lend itself to a large number of burnersof small fuel capacity.

From the foregoing description of the invention, itis evident that sucha furnace structure is adapted to maintain uniform heat of billets,ifngots, slabs or the like in an economical manner as its regularuniform external wall surface requires a minimum input of heat and isadapte'd to the utilization of the cheaper fuels. By recirculating partof the preheated air, the tile 80 at the exhaust end of the recuperatorpassages is maintained at suitable temperatures and Ya. high preheat isavailable for eillcient and economical firing- Although an embodiment ofthe invention has been herein illustrated and described, it will beevident that various modifications may be made in the details ofconstruction and in the arrangement of parts without departing from'theprinciples herein set forth. It is also apparent that the method of mingand heat control is applicable to continuous heating of articles otherthan billets, slabs or the like.

We claim:

1. A continuous heating furnace comprising an elongated heating chamberhaving Aan inclined roof from the charging end towards the discharge endof the chamber and an inclined roof from the discharge end towards thecharging end forming an apex remote from the charging end and near thedischarge end of the chamber, a hearth disposed within the chamber belowthe end of the roof-at the charging end and above the end of the roof atthe discharge end, an exhaust passage adjacent the charging anddischarge ends of said chamber extending beneath the hearth and meansfor withdrawing the products of combustion from the chamber in dividedpaths through the said exhaust passages.

2. A continuous heating furnace comprising an elongated heating chamberhaving charge and discharge openings at opposite ends, a hearthextending longitudinally of the chamber, exhaust passages in saidhearth, recuperator tile structures beneath said hearth communicatingwith said exhaust passages and separated by partition walls dividing therecuperator structures in separately controllable sections, burner portsin said heating chamber, means for withdrawing therproducts ofcombustion through the exhaust passages direct to the stack, means forconducting the products of combustion through said re-y cuperatorsections, means for4 directing air through the recuperator structures inheat exchange relation with the waste gas passages, means for conductingthe preheated air from the recuperator structures to the burner port,

and means between the recuperator and the furnace for regulating thevolume of air supplied to the furnace independent of that supplied tothe recuperator sections.

3.`A continuous heating furnace comprising an elongated heating chamberhaving an inclined roof extending from a maximum elevation at a portionof the chamber near the discharge end thereof tothe charge and dischargeopenings of the chamber, a burnr disposed through the roof adjacent theapex thereof disposed to direct a heat flame toward the hearth in thedirection of the'charging end of the furnace chamber, a plurality ofrecuperator structures beneath the hearth of the heating chamber, anexhaust passage adjacent the discharge end of the furnace with the mouthof the passage above the discharge opening of the chamber, said exhaustpassage being vin communication with said recuperator structures, anexhaust passage adjacent the charging end of the chamber incommunication with the recuperator structures, means for withdrawing theproducts of combustion from the heating chamber through the severalexhaust passages and their respective recuperator structures, means forsupplying air tothe recuperators and for withdrawing the preheated airthrough a passage leading to the burner ports, and means forindependently regulating the quantity of cold and heated air supplied todifferent portions of the recuperator structures.

4. A continuous heating furnace comprising an elongated chamber having aat arch roof sloping frcm a maximum elevation near the discharge end ofthe chamber towards a charge and discharge opening at opposite ends ofthe chamber, a lrecuperator structure beneath the hearth of saidchamber, an exhaust passage adjacent the charging and discharge ends ofthe chamber extending beneath the hearth and communicating with therecuperator structure, lexfhaust means for withdrawing the pr`ducts ofcombustion from the -heating chamber through the exhaust passages inregulable amounts and .passages extending through the from the exhaustpassages through the recuperator structures to a stack, means forsupplying air to the bottom of the recuperator structures, and means forcollecting the preheated air from the recuperator structures near thetop thereofr and conducting it to the burner ports of the heatingchamber.

5. A continuous heating furnace comprising an elongated heating chamberhaving a charging and discharge opening at opposite ends, exhaust hearthadjacent the charge and discharge openings, an exhaust passage extendingthrough the hearth intermediate said flrst named passages, a recuperatorstructure beneath the hearth of the heating chamber in communicationwith the exhaust passages of the chamber, partition walls dividing saidrecuperator structures into independently controllable units for therespective exhaust passages, means for by-passing the products ofcombustion around said recuperator structures to a stack and means formoving the products of combustion through the exhaust passages andcontrolling the movement at will in the respective recuperatorstructures to the stack, means for supplying air to the recuperatorstructures, means for collectingv the preheated air from all of therecuperator structures and conducting it in heat exchange relation withthe exhaust passages of the chamber to the burner ports, and means forregulating the quantity of air supplied to the several recuperatorsections.

6. A continuous heating furnace comprising an elongated chamber havingcharge and discharge openings at opposite ends and having exhaustpassages extending through the hearth, the discharge passage of thechamber being below the level of the hearth, burner ports disposed inthe roof of the chamber for directing a heating flame towards the hearthand in the direction of the charging end of the furnace chamber, arecuperator structure beneath the hearth. means for withdrawing theproducts of combustion through the exhaust passages into the recuperatorstructure, and thence to a stack, means for supplying air to therecuperator structures at the bottom thereof and withdrawing thepreheated air` same through the air preheat passages of the recuperatorstructures.

7. A continuous heating furnace comprising an elongated heating chamberhaving parallel skids for a portion of its length to support thearticles to be heated in spaced relation with the hearth, said skidmembers terminating in a solid hearth portion near` the discharge end ofthe furnace whereby' the articles to be heated are initially conveyedalong the skid vmembers and subsequently on the solid hearth portion,burners in said chamber below and above said skid mem- .'bers, theburners being located to direct a heating flame on the work atsubstantially the juncture of the skid members and solid hearthv`portion, and means for withdrawing the products of combustion in desiredvolumes from the top burners, to eiect a division thereof atsubstantially the juncture of the skid members and the said solid hearthportion.

8. `A continuous heating furnace'comprising an elongated heating chamberhaving its roof wall adjacent the discharge the respective ends of "thedischarge end being beneath tension with said skid members beneath theapex f of the furnace roof and sloping sharply downward to the dischargeopening of the furnace, heating means comprising a gaseous burnerextending through the roof of the furnace above the work-supportinghearth that constitutes a continuationv of the skid members, burnersbeneath said skid members and means beneath the hearth and` skid membersfor withdrawing the products of combustion from the gaseous burner lndivided paths towards the respective ends of the furnace chamber.

9. A continuous heating furnace having a work-supporting hearthsubstantially horizontal throughout one end of said hearth decliningsharply to constitute. a discharge chute for the articles passingthrough the furnace, a combustion chamber provided above said hearth andwaste gas passages beneath the hearth at the respective ends thereof,the waste gas passage at the inclined portion of the hearth and abovethe discharge opening of the furnace chamber.

10. A continuous heating furnace having a work-supporting hearthsubstantially horizontal throughout one end of said hearth decliningsharply to constitute a discharge chute for the articles passing throughthe furnace, a combustion chamber provided above said hearth and wastegas passages beneath the hearth at the respective ends thereof, thewaste gas passage at the discharge end being beneath the inclinedportion of the hearth and above the discharge opening of the furnacechamber, and regulable means controlling the exhaustion of the productsof combustion from the heating chamber through the said Waste gaspassages.

1l. A continuous heating furnace comprising a heating chamber and avhearth with a charging opening at one end and a discharge opening atthe opposite end,- a product-supporting hearth extending longitudinallyof said chamber andl having-its upper level coextensive with thecharging opening and above the discharge opening, burners disposedintermediate the charge and 'discharge ends of said `chambers. andexhaust means for withdrawing products of combustion in desiredquantities simultaneously at diiferent points across the hearth of thefurnace adjacent the discharge end.

12. A continuous heating furnace comprising a heating chamber and ahearth with a charging opening at one end and a discharge opening at theopposite end, a product supporting hearth extending longitudinally ofsaid chamber and having its upper level coextensive with the chargingopening and above the discharge opening, burners disposed intermediatethe charge and discharge ends of said chamber, and spaced dampercontrolled exhaust means adjacent the discharge end of the furnace andconnected thereto substantially beneath the hearth for withdrawingproducts of combustion from the furnace.

13. A continuous heating furnace compris' .g an elongated heatingchamber having an inclined roof from the charging end towards thedischarge end of -the chamber and an inclined roof from the dischargeend towards the charging end forming an apex remate frombthe chargingend and near the discharge end of the chamber, a hearth disposed withinthe chamber below the end o1' the roof at the charging end and above theend of the roof at the discharge end, an exhaust passage adjacent thecharging and discharge ends of said chamber and an exhaust passageintermediate said end exhaust passages, said exhaust passages extendingbeneath the hearth, and means for withdrawing the prcducts of combustionfrom the \chamber selectively in divided paths through the

